Fix crash after paste and unmount (#100589)

packages/flutter/lib/src/widgets/editable_text.dart

@@ -1740,7 +1740,9 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     if (cause == SelectionChangedCause.toolbar) {
       // Schedule a call to bringIntoView() after renderEditable updates.
       SchedulerBinding.instance.addPostFrameCallback((_) {
-        bringIntoView(textEditingValue.selection.extent);
+        if (mounted) {
+          bringIntoView(textEditingValue.selection.extent);
+        }
       });
       hideToolbar();
     }

packages/flutter/test/widgets/editable_text_test.dart

@@ -11798,6 +11798,56 @@ void main() {
     await tester.pump();
     expect(receivedIntent, isFalse);
   });
+
+  // Regression test for https://github.com/flutter/flutter/issues/100585.
+  testWidgets('can paste and remove field', (WidgetTester tester) async {
+    final TextEditingController controller = TextEditingController(text: 'text');
+    late StateSetter setState;
+    bool showField = true;
+    final _PasteTextSelectionControls controls = _PasteTextSelectionControls(
+      onPaste: () {
+        setState(() {
+          showField = false;
+        });
+      },
+    );
+    await tester.pumpWidget(MaterialApp(
+      home: StatefulBuilder(
+        builder: (BuildContext context, StateSetter stateSetter) {
+          setState = stateSetter;
+          if (!showField) {
+            return const Placeholder();
+          }
+          return EditableText(
+            backgroundCursorColor: Colors.grey,
+            controller: controller,
+            focusNode: focusNode,
+            style: textStyle,
+            cursorColor: cursorColor,
+            selectionControls: controls,
+          );
+        },
+      ),
+    ));
+
+    await tester.tap(find.byType(EditableText));
+    await tester.pump();
+
+    final EditableTextState state =
+        tester.state<EditableTextState>(find.byType(EditableText));
+
+    await tester.longPress(find.byType(EditableText));
+    await tester.pump();
+    expect(state.showToolbar(), isTrue);
+    await tester.pumpAndSettle();
+    expect(find.text('Paste'), findsOneWidget);
+
+    await tester.tap(find.text('Paste'));
+    await tester.pumpAndSettle();
+
+    expect(tester.takeException(), null);
+  // On web, the text selection toolbar paste button is handled by the browser.
+  }, skip: kIsWeb); // [intended]
 }
 
 class UnsettableController extends TextEditingController {
@@ -11911,6 +11961,106 @@ class MockTextSelectionControls extends Fake implements TextSelectionControls {
   }
 }
 
+// Fake text selection controls that call a callback when paste happens.
+class _PasteTextSelectionControls extends TextSelectionControls {
+  _PasteTextSelectionControls({
+    required this.onPaste,
+  });
+
+  static const double _kToolbarContentDistanceBelow = 20.0;
+  static const double _kToolbarContentDistance = 8.0;
+
+  final VoidCallback onPaste;
+
+  @override
+  Widget buildToolbar(BuildContext context, Rect globalEditableRegion, double textLineHeight, Offset position, List<TextSelectionPoint> endpoints, TextSelectionDelegate delegate, ClipboardStatusNotifier? clipboardStatus, Offset? lastSecondaryTapDownPosition) {
+    final Offset selectionMidpoint = position;
+    final TextSelectionPoint startTextSelectionPoint = endpoints[0];
+    final TextSelectionPoint endTextSelectionPoint = endpoints.length > 1
+      ? endpoints[1]
+      : endpoints[0];
+    final Offset anchorAbove = Offset(
+      globalEditableRegion.left + selectionMidpoint.dx,
+      globalEditableRegion.top + startTextSelectionPoint.point.dy - textLineHeight - _kToolbarContentDistance
+    );
+    final Offset anchorBelow = Offset(
+      globalEditableRegion.left + selectionMidpoint.dx,
+      globalEditableRegion.top + endTextSelectionPoint.point.dy + _kToolbarContentDistanceBelow,
+    );
+    return _PasteTextSelectionToolbar(
+      anchorAbove: anchorAbove,
+      anchorBelow: anchorBelow,
+      handlePaste: () => handlePaste(delegate),
+    );
+  }
+
+  @override
+  Widget buildHandle(BuildContext context, TextSelectionHandleType type, double textLineHeight, [VoidCallback? onTap]) {
+    return Container();
+  }
+
+  @override
+  Size getHandleSize(double textLineHeight) {
+    return Size.zero;
+  }
+
+  @override
+  Offset getHandleAnchor(TextSelectionHandleType type, double textLineHeight) {
+    return Offset.zero;
+  }
+
+  @override
+  bool canPaste(TextSelectionDelegate delegate) {
+    return true;
+  }
+
+  @override
+  Future<void> handlePaste(TextSelectionDelegate delegate) {
+    onPaste();
+    return super.handlePaste(delegate);
+  }
+}
+
+// A fake text selection toolbar with only a paste button.
+class _PasteTextSelectionToolbar extends StatefulWidget {
+  const _PasteTextSelectionToolbar({
+    Key? key,
+    required this.anchorAbove,
+    required this.anchorBelow,
+    this.handlePaste,
+  }) : super(key: key);
+
+  final Offset anchorAbove;
+  final Offset anchorBelow;
+  final VoidCallback? handlePaste;
+
+  @override
+  _PasteTextSelectionToolbarState createState() => _PasteTextSelectionToolbarState();
+}
+
+class _PasteTextSelectionToolbarState extends State<_PasteTextSelectionToolbar> {
+  @override
+  Widget build(BuildContext context) {
+    return TextSelectionToolbar(
+      anchorAbove: widget.anchorAbove,
+      anchorBelow: widget.anchorBelow,
+      toolbarBuilder: (BuildContext context, Widget child) {
+        return Container(
+          color: Colors.pink,
+          child: child,
+        );
+      },
+      children: <Widget>[
+        TextSelectionToolbarTextButton(
+          padding: TextSelectionToolbarTextButton.getPadding(0, 1),
+          onPressed: widget.handlePaste,
+          child: const Text('Paste'),
+        ),
+      ],
+    );
+  }
+}
+
 class CustomStyleEditableText extends EditableText {
   CustomStyleEditableText({
     Key? key,